Role of reactive oxygen species (ROS) in MAPK-mediated chemotropism and infectious growth of the plant pathogenic fungus Fusarium oxysporum

趋化性是指真菌的生长向化学梯度方向发展，它控制着真菌的基本过程，如营养获取、有性或无性融合和宿主感染。化学引诱物分子的性质以及趋化性受体和下游信号传导途径在很大程度上是未知的。科尔多瓦大学的宿主组开发了一种定量测量真菌植物病原体尖孢镰刀菌中定向菌丝生长的方法。对趋化性机制的遗传解剖导致了丝裂原活化蛋白激酶（MAPK）Mpk1的鉴定，Mpk1是F.尖孢菌对寄主植物的信号传递。此外，根分泌物中的主要化学引诱物被确定为植物分泌的过氧化物酶，这表明活性氧（ROS）在MAPK介导的趋化性信号转导中的作用。本研究拟通过测定丝裂原活化蛋白激酶（MAPK）的磷酸化状态和趋化性反应，研究ROS产生酶NADPH氧化酶（Nox）在丝裂原活化蛋白激酶（MAPK）信号转导和趋化性生长中的作用。尖孢菌nox缺失突变体和2）使用次磺酸状态下的半胱氨酸捕获和定点诱变来鉴定通过过氧化物酶的ROS依赖性活性修饰的真菌靶蛋白。我们预计，这些结果将揭示新的分子联系和下游目标的ROS和MAPK信号转导的基本过程中指导真菌致病性。这些知识将对开发新的抗真菌药物感兴趣。总的来说，该项目结合了申请人和主办机构关于真菌和趋化性生长中ROS信号传导的经验。此外，它允许申请人在国际公认的研究小组中从事前沿研究课题，为她在未来几年在德国进行创新研究做好最佳准备。

Chemotropism, the directed growth towards a chemical gradient, governs essential processes in fungi such as nutrient acquisition, sexual or asexual fusion and host infection. The nature of the chemoattractant molecules, as well as the chemotropic receptors and downstream signaling pathways are largely unknown. The host group at University of Córdoba has developed a method to quantitatively measure directed hyphal growth in the fungal plant pathogen Fusarium oxysporum. Genetic dissection of the chemotropic mechanism led to the identification of a mitogen-activated protein kinase (MAPK), Mpk1, as an essential component in the chemotropic response of F. oxysporum to host plant signals. Moreover, the major chemoattractant in root exudates was identified as a plant-secreted peroxidase, suggesting a role of reactive oxygen species (ROS) in MAPK-mediated chemotropic signaling. Here we propose to 1) study the role of the ROS-generating enzymes NADPH oxidases (Nox) in regulation of MAPK signaling and chemotropic growth, by determining MAPK phosphorylation status and chemotropic response in F. oxysporum nox deletion mutants and 2) to identify fungal target proteins that are modified by the ROS-dependent activity of the peroxidase, using cysteine trapping in sulfenic acid state and site-directed mutagenesis. We anticipate that the results will uncover novel molecular links and downstream targets of ROS and MAPK signaling in fundamental processes guiding fungal pathogenicity. This knowledge will be of interest for the development of new anti-fungal drugs. Overall, this project combines the experiences of the applicant and the host institute regarding ROS signaling in fungi and chemotropic growth, respectively. Further, it allows the applicant to work on a cutting-edge research topic in an internationally recognized research group providing her with optimal preparation to undertake innovative research in Germany in the upcoming years.